Old steel panel rads of 60s/70s without fins

[John Stumbles]

[I'm posting this to the group as it was emailed to me from someone who presumably found my article on rad outputs on the wiki.]

I have been searching for these specs since I had my old ones replaced by modern convectors in Feb this year with DISASTEROUS RESULTS. Those old steel panel rads with no fins had amazing radiaant heat transfer properties, and I did not know that they just needed FLUSHING THROUGH, or what benefits they had over the modern convectors, until I changed them, to my great regret, too late. I did find a website which gave the heat output for the old obsolete rads, and found that my 58cm high and about 47inch something wide old ones had a wattage of about 1000. Similar modern ones today, are 752W with no fins. Researched that" the powers that be "have thinned the steel down over the years and my new ones are the now new regs of 1.20mm of cold rolled steel plate, which do get hot but do not radiate or give off the intense heat that my old ones did. Also the INERTIA has been reduced to make the rads lose their heat quicker, and so do I! My old ones kept hot for a very long time and reduced their heat very slowly, enabling me to turn off boiler at a low air temp. of 20.5, and I remained warm for 90 minutes, 20 mins after the rads were cold. Very energy saving. With my new convectors, I and all my FEMALE friends and relatives, do not feel even warm enough at 24 degrees, and as rads lose their heat quicker, I keep shivering, which I never did at a much lower air temp, with my old little miracles I lost. And the new energy saving boiler had to be on constantly, drying out the air, but still not getting me warm at even 26 degree AIR TEMP> Humidity in room went down to 29% and I had a dry mouth breathing in the uncomfortable too dry air. My old ones gave me a healthy humidity of 48% at 21 degrees, and cosy warmth. You are a man, and do not feel the cold as much as we females, or react to sudden loss of heat as we do - the men I know say they always hot. Also, I was surprised that, with my old ones, the night min. temp in my front room, which is all glass and open plan to a glass front door and 9 squ m unheated kitchen, with just 1" of glass wool in the ceiling of my bungalow, lost only 2 degrees ( from 20.5 - 18.6), during -4 degrees of frost in the night, with no heating on. But my convectors cannot do this, and with +6 min in the night, my front room min temp went down by 10 degrees!!!!!! My rearch on the web, explained to me that the old rads gave off a powerful direct to the body heat, which also warmed the walls and solid objects, which convectors are not good at doing, and the walls gave back their heat in the night when the ambient air temp reduced. My scientific brother, who worked on aero combustion, said radiators all work by convection, NEVER by radiation, as that is only possible with electric, open fire flame or sources from the sun!!!!!!!!!!!! And is insisting that the old rads could not be any different from the new ones. I know they have made the steel thinner and indeed they sound more like TIN when tapped. The old ones CLONKED. so I have been trying to find the specs on the old ones to prove to my brother than I am not insane!!! And the water content has been lowered, so heat output is lowered. I found a website, which explained everything that happened when I changed my old non-finned rads for convectors, and that is Energy Saving Now, with particular reference to " The mess with radiators" Also the shivering was explained in one of the other sections, about heat from the fins of convectors losing heat quicker than the waterfilled panals, and the body reacting by "feeling a sudden freezing" and reaching for room thermostat to bring on the heating again so soon. using more gas than is necessary with the non-finned rads. Which is exactly what I did. He especially refers to the benefits of the old obsolete rads for older not so well insulated houses, and the inappropriateness of convectors in such houses. He went as far to say that "science had got it wrong to make them obsolete, by deeming them inefficient". I have learned this all too late. After the flushing through of the old ones, they gave out such a powerful direct to body heat that even the plumber thought the rooms were 10 degrees higher than my thermometers said, and in his ignorance, he claimed my thermometers were all wrong, which they were not. So, my message for you is that the old obsolete rads are BETTER than the new convectors whether for old or new houses. And to keep them as long as they last. In fact, I have been searching to find these old rads to swop with my new ones, but in vain I would be very interested in any pecs you have of the 60s and 70s rads, to prove to my brother how they HAVE changed. He has 1984 rads, most without fins, including a double with no fins, but has no way of knowing their technical heat outputs, but assumed what they were, from comparing them with today's - grave error, as the sizes have reduced their output. I read on one website that in 1997, new regs forced rads to reduce their output by 11% and asked WHY? But there was no answer. Do not know if you will receive this e-mail as I wanted to reply on the website, but too complicated for me to LOG IN, I,m afraid.

[Reminder: the above is what was emailed to me, not my own words]

[dennis]

8<

Do you think he was ill or a troll? Almost nothing was likely to be true.

[tony sayer]

Well thats all rather scientific in its approach so you can now make energy disappear;!..

[meow2222]

Lot of confusion of course, but its not all wrong. Adding fins increases convection, changing the radiation/convenction ratio. And yes, lower water volume rads will cool faster between boiler firings, the 2 factors resulting in lower minimum radiated heat levels.

To restore greater evenness of temp one can arrange for the boiler to fire more frequently, by reducing the hysteresis of the stat. This can be done by changing from a bimetal stat to an electronic one.

NT

[Roger Mills]

Is it worth answering, I ask myself. Probably not, but I'm going to anyway!

I'm afraid that the above outpouring demonstrates a complete lack of understanding of the laws of physics.

The heat given out by a radiator depends almost entirely on its surface area and on its mean temperature relative to room temperature (delta-T). The thickness of the steel from which it is constructed matters not one iota. Size for size, a radiator with fins will give out more heat by convection than one without because of the increased surface area over which the convected air passes. The heat radiated (which is relatively small compared with convected heat) will be much the same between finned and unfinned radiators.

It is true that radiator manufacturers are now quoting lower output figures for a given size and construction of radiator than they used to. This is

*purely* because they are quoting the output at a lower delta-T value to relect the fact that modern condensing boilers run at a lower water temperature than 'conventional' boilers. Hence, if you replace a conventional boiler with a condensing model - and run that at its most efficient condition - radiators which were previously adequate may no longer be so, and may need to be replaced by larger ones - or by rads of the same size but with fins.

The OP's problem is almost certainly down to incorrectly spec'd finned radiators for use with the new boiler rather than to there being anything inherently wrong with finned radiators.

[dennis]

However add in the "they keep me warm for 20 minutes after the radiators have gone cold" and you quickly wonder why he needs the rads at all and why it should be any different whichever rads have gone cold.

Just as well really as I use skirting heating and that only holds a bit of water. You don't want much water in a heating system, you want quick response and close control. A lot of water is slow to heat up and slow to cool down making temperature swings almost inevitable. Mine just sits there at about +-0.5C.

[Rod]

Hmmm, there is a reason for people, especially women, to be shivering and cold at 24 C. Have a look at my sig. :-)

Partner used to suffer similarly to the emailer (but would put on extra layers or whatever rather than overheat the room to 26 C), and got worse each year, until the illness was diagnosed.

[Ed Sirett]

My guess is that the old system was being run with higher average temperatures. With the radiation/convection balance being so sensitive to changes in the radiator temperature. Many of the effects would be as observed by the winger oops customer.

Sounds like some one who would feel more comfortable with a source of radient heat like a fire.